Figure 4.

Carbon isotope discrimination (Δ¹³C) is physiologically linked to WUE. A, Association of kernel Δ¹³C (Δ¹³C_Kernel) and intrinsic WUE (iWUE) measured at stage V5/6 in different experiments (Exp. 1–3) and genotypes (data from Figures 1, 3, and 4B. Data from near-isogenic lines (NILs) carrying the recurrent parent (RP) ZmAbh4 allele or the NIL B allele, and from abh4 CRISPR mutants (abh4 mut) and their wild types (WT) are shown). Plants were grown in a greenhouse for Exp. 1 and 3 and in a growth chamber for Exp. 2. Shown are means ± SE for each genotype per experiment. B, Δ¹³C derived from isotopic compositions of dry matter (Δ¹³C_Kernel, n = 9 plants; Δ¹³C_Leaf, n = 17–18 plants) and photosynthetic Δ¹³C (Δ¹³C_{Photosynthetic}, n = 14 plants) from online gas exchange measurements for RP and NIL B. Bars indicate mean ± SE. Significant differences compared to RP based on two-sided Student’s t test are indicated by ***P < 0.001. C, Relationship between Δ¹³C_{Photosynthetic} and concurrently measured ratio of intercellular to ambient CO₂ concentration (C_i/C_a) in RP and NIL B.